The room, which often is used for public hearings, will be shut for at least a week while repairs are made.

Similar problems were found a few weeks back in old beams above Mayor Bloomberg's "bullpen," where the mayor and his top deputies work. A $5.5 million fixup is underway there.

Built from 1803-12, tiny City Hall still houses both the mayor and Council. Most Council hearings are held in its Chamber, long in need of a major overhaul. The adjoining committee room is used for hearings when the Chamber is booked. Hearings that were to be held there next week have been shifted to rooms across the street at 250 Broadway.